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to retract or extend the landing gear using the left hydraulic system.
GEAR EXTENSION
During gear extension, the NLG extends rearward and the MLG extends outward.
When the landing gear switch is manually selected to the DN position, the PSEU commands and monitors the following
events:
- Landing gear selector valve is energized to direct hydraulic fluid to release the MLG uplocks and the nose overcenter
mechanism, extending the landing gear
- NLG and MLG downlocks are hydraulically and mechanically engaged to secure the landing gear in the extended
position.
GEAR RETRACTION
During retraction, the nose gear retracts forward and the main gear retracts inward.
During landing gear retraction (no WOW signal), the PSEU commands and monitors the following events:
- Landing gear selector valve is energized to direct hydraulic fluid to release the respective downlocks and retract
the NLG and MLG. The brake control unit (BCU) commands a brake pressure of 350 psi for four seconds during
gear retraction to ensure the main wheels have stopped spinning as they enter the MLG bay.
- When the gear is fully up, uplocks for the MLG are engaged mechanically. The uplock mechanism consists of a
housing bolted to the airframe structure containing a latch lever and hook that engages a roller attached to the
steering cuff of the landing gear. The hook holds the NLG in the retracted position.
- A restrictor is located in the aft of the NLG wheel well. This restrictor is installed in the up hydraulic line. When
the landing gear selector handle is selected UP, this restrictor will decrease hydraulic fluid flow which decreases
the retraction speed and allows the NLG to retract smoothly and with less noise.
LANDING GEAR
Volume 2 Flight Crew Operating Manual Sep 13/2004
15-01-10 CSP 100-6 REV 1
LANDING GEAR (Cont)
MANUAL RELEASE SYSTEM (MRS)
Should a failure occur with the landing gear control circuitry or the left hydraulic system, the manual release system is
available to the crew as an alternate means to extend the landing gear. Upon release from the uplock, the nose landing gear
will fully extend with the aid of gravity and spring forces, while the auxiliary extend actuators assist in the extension of the
main landing gear.
The handle is located near the rear of the center pedestal on the copilot’s side. When the manual release handle is operated
by the aircrew, cable movement is transmitted through the main quadrant, by a closed loop cable assembly to the main landing
gear quadrant, and MLG valve assemblies. The displacement of the spools on the two dump valves blocks the supply
of hydraulic pressure and connects the downstream landing gear components via the return lines to the left hydraulic system
reservoir and bypasses the landing gear actuators. The MLG quadrant operates the MLG uplock manual release levers via
tension cables. Displacement of the uplocks releases the MLGs for gravity extension.
The manual selector valve, when activated by the MLG quadrant, admits pressure from the right hydraulic system (supported
by an accumulator) to both auxiliary extend actuators to assist the main landing gear into downlock. The mechanical
locks in the side brace actuator then engage and lock the gear down. During normal operation, the auxiliary extend actuators
are bypassed to the right hydraulic system return and the piston moves freely as the landing gear extend and retract.
Manual release handle movement is transmitted from the main quadrant to the manual release lever on the NLG uplock.
The uplock releases and the NLG extends to the down and locked position.
By moving the manual release handle to the stowed position the landing gear extension and retraction system is reset for
normal operation. However, landing gear retraction will only be initiated when the landing gear handle is moved to the UP
position. After an actual gear failure situation, the manual release handle should be stowed only after landing and the gear
pins are installed.
PUSH
TO
STOW
LG PULL
CFO1501002_017
LANDING GEAR
Sep 13/2004 Flight Crew Operating Manual Volume 2
REV 1 CSP 100-6 15-01-11
TIRES AND BRAKES
DESCRIPTION
The Challenger 300 uses dual wheel assemblies and brakes on each main landing gear. The speed limit of all tires is 182 kt.
The nose gear has two wheels and uses chine tires to eject the ground water away from the aircraft engines.
To prevent tire burst, each main wheel has four heat sensitive fusible plugs. They melt when heat buildup in the wheel/tire
assembly exceeds a preset value, permitting the tire to deflate safely.
The PARK/EMER BRAKE handle, located on center pedestal, is controlled from within the flight compartment. Anti-skid
is not available when utilizing emergency brakes.
　
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